local _M = require "alien_c"
local alien = _M
local io = require "io"

local pairs, ipairs = pairs, ipairs
local setmetatable = setmetatable
local error = error
local pcall = pcall
local type = type
local rawset = rawset
local unpack = unpack
local math = math

local load, callback = alien.load, alien.callback

_M.loaded = {}

local load_library, find_library = {}, {}

local function find_library_helper(libname, opt)
  local expr = '/[^() ]*lib' .. libname .. '%.so[^() ]*'
  local cmd = '/sbin/ldconfig ' .. opt ..
    ' 2>/dev/null | egrep -o "' .. expr .. '"'
  local pipe = io.popen(cmd)
  if pipe then
    local res = pipe:read()
    pipe:close()
    return res and res:match("([^%s]*)")
  end
  return nil
end

function find_library.linux(libname)
  return find_library_helper(libname, "-p")
end

function find_library.bsd(libname)
  return find_library_helper(libname, "-r")
end

function find_library.darwin(libname)
  local ok, lib = pcall(load, libname .. ".dylib")
  if ok then return lib end
  ok, lib = pcall(load, libname .. ".framework/" .. libname)
  if ok then return lib end
  return nil
end

local function load_library_helper(libname, libext)
  if libname:match("/") or libname:match("%" .. libext) then
    return load(libname)
  else
    local ok, lib = pcall(load, "lib" .. libname .. libext)
    if not ok then
      ok, lib = pcall(load, "./lib" .. libname .. libext)
      if not ok then
        local name = find_library[alien.platform](libname)
        if name then
          lib = load(name)
        else
          return nil, "library " .. libname .. " not found"
        end
      end
    end
    return lib
  end
end

function load_library.linux(libname)
  local lib, errmsg = load_library_helper(libname, ".so")
  if not lib then error (errmsg) end
  return lib
end

load_library.bsd = load_library.linux

function load_library.darwin(libname)
  local lib, errmsg = load_library_helper(libname, ".dylib")
  if not lib then
    lib, errmsg = load_library_helper(libname, ".so")
  end
  if not lib then error (errmsg) end
  return lib
end

function load_library.windows(libname)
  return load(libname)
end

setmetatable(_M.loaded, { __index = function (t, libname)
                                      local lib = load_library[alien.platform](libname)
                                      t[libname] = lib
                                      return lib
                                    end, __mode = "kv" })

function _M.load(libname)
  return _M.loaded[libname]
end

function _M.callback(f, ...)
  local cb = callback(f)
  cb.types(cb, ...)
  return cb
end

local array_methods = {}

local function array_next(arr, i)
  if i < arr.length then
    return i + 1, arr[i + 1]
  else
    return nil
  end
end

function array_methods:ipairs()
  return array_next, self, 0
end

function array_methods:realloc(newlen)
  self.buffer:realloc(newlen * self.size)
  self.length = newlen
end

local function array_get(arr, key)
  if type(key) == "number" then
    if key < 1 or key > arr.length then
      error("array access out of bounds")
    end
    local offset = (key - 1) * arr.size + 1
    return arr.buffer:get(offset, arr.type)
  else
    return array_methods[key]
  end
end

local function array_set(arr, key, val)
  if type(key) == "number" then
    if key < 1 or key > arr.length then
      error("array access out of bounds")
    end
    local offset = (key - 1) * arr.size + 1
    arr.buffer:set(offset, val, arr.type)
    if arr.type == "pointer" then
      arr.pinned[key] = val
    end
  else
    rawset(arr, key, val)
  end
end

function _M.array(t, length, init)
  local ok, size = pcall(alien.sizeof, t)
  if not ok then
    error("type " .. t .. " does not exist")
  end
  if type(length) == "table" then
    init = length
    length = #length
  end
  local arr = { type = t, length = length, size = size, pinned = {} }
  -- FIXME: When Lua 5.1 support is dropped, add a __len metamethod
  setmetatable(arr, { __index = array_get, __newindex = array_set })
  if type(init) == "userdata" then
    arr.buffer = init
  else
    arr.buffer = alien.buffer(size * length)
    if type(init) == "table" then
      for i = 1, length do
        if type(init[i]) == "string" then
          local offset = (i - 1) * size + 1
          arr.pinned[i] = alien.buffer(#init[i] + 1)
          arr.buffer:set(offset, arr.pinned[i], "pointer")
        end
        arr[i] = init[i]
      end
    end
  end
  return arr
end

local function struct_new(s_proto, ptr)
  local buf = alien.buffer(ptr or s_proto.size)
  local function struct_get(_, key)
    if s_proto.offsets[key] then
      return buf:get(s_proto.offsets[key] + 1, s_proto.types[key])
    else
      error("field " .. key .. " does not exist")
    end
  end
  local function struct_set(_, key, val)
    if s_proto.offsets[key] then
      buf:set(s_proto.offsets[key] + 1, val, s_proto.types[key])
    else
      error("field " .. key .. " does not exist")
    end
  end
  return setmetatable({}, { __index = struct_get, __newindex = struct_set,
                            __call = function () return buf end })
end

local function struct_byval(s_proto)
  local types = {}
  local size = s_proto.size
  for i = 0, size - 1, 4 do
    if size - i == 1 then
      types[#types + 1] = "char"
    elseif size - i == 2 then
      types[#types + 1] = "short"
    else
      types[#types + 1] = "int"
    end
  end
  return unpack(types)
end

function _M.defstruct(t)
  local off = 0
  local names, offsets, types = {}, {}, {}
  for _, field in ipairs(t) do
    local name, type = field[1], field[2]
    names[#names + 1] = name
    off = math.ceil(off / alien.align(type)) * alien.align(type)
    offsets[name] = off
    types[name] = type
    off = off + alien.sizeof(type)
  end
  return { names = names, offsets = offsets, types = types, size = off, new = struct_new,
           byval = struct_byval }
end

function _M.byval(buf)
  if buf.size then
    local size = buf.size
    local types = { "char", "short"}
    local vals = {}
    for i = 1, size, 4 do
      if size - i == 0 then
        vals[#vals + 1] = buf:get(i, "char")
      elseif size - i == 1 then
        vals[#vals + 1] = buf:get(i, "short")
      else
        vals[#vals + 1] = buf:get(i, "int")
      end
    end
    return unpack(vals)
  else
    error("this type of buffer can't be passed by value")
  end
end